( er to better eliminate the false positi...)Screening of Corticosteroids in Urine by Negative Atmospheric Pressure Chemical Ionization LC/MS/MS

er to better eliminate the false positives. Only cortisone and hydrocortisone, which are endogenous corticosteroids, are monitored with one ion. Three ions were not used in order not to increase the scan time. The confirmation of the positive sample can be done by a confirmation method specific for the suspected corticosteroid monitoring at least three of its MS/MS transitions.

Particular care was taken to separate the prednisolone from cortisone. The two corticosteroids have the same molecular masses, and cortisone gives an abundant peak on the transition (-) 419.2>329 of prednisolone. The triamcinolone acetonide-flunisolide and fluorometholone-desoximethasone pairs also share their transitions, but are separated by their retention times. The epimeres betamethasone and dexamethasone have similar retention times and mass spectra, and they could not be separated in the LC/MS conditions described.

Figure 1 (page 3) shows the LC/MS analysis of a blank urine sample spiked with 20 ng/mL of each corticosteroid (except cortisone and hydrocortisone, which are endogenous) and 200 ng/mL internal standard. There are no matrix interferences, and the abundances and signal/noise ratios are satisfactory for all compounds of interest even with a standard gain of the detector. In order to increase the reliability of the result, the confirmation of a positive sample can be done with the detector set on high gain.

Conclusion

The LC/MS/MS method described in this application note is simple and sensitive. In one run this method can screen for 17 corticosteroids and easily detect them below the WADAs MRPL, 30 ng/mL. The Varian 1200L system proved to be an essential tool for a doping control laboratory.

References

1. Hardmann, J.G.; Limbird, E.J., The Pharmacological Basis of Therapeutics (9th edn). New York, 1996

2. Polettini, A.; M
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